${9 \div 0.1 = {?}}$
Answer: $ {9 \div 0.1 = 9 \div \dfrac{1}{10}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {9 \div \dfrac{1}{10} = 9 \times \dfrac{10}{1}} $ $ {\phantom{9 \div \dfrac{1}{10}} = 90} $